2 
of the images with a least reading of one micron. The system consists 
of an operator's console with reference unit, two comparator units, 
and a three-unit electronic rack. 
Operationally, the operator has the option of controlling the 
instrument manually or automatically. In the manual mode, the 
operator drives the tables to the area of the pass point using joy 
stick control. Then by viewing the superimposed images on the monitor 
scope or viewing the conjugate imagery in the binocular viewer, he 
selects the precise conjugate of the pass point. In the automatic 
mode, correlation techniques are used to slave the tables such that 
conjugate images are always being obtained. The operator manually 
controls one table designated as the "master" and the other through 
the electronic correlation circuitry follows as the "slave." The 
operator slews between points in a coarse or rapid mode. When he 
arrives at the pass point area, he changes to a fine or slow speed 
mode and directs the master to the desired point. When correlation 
is complete, a mark and record button is depressed and the pass point 
is marked and recorded. The operator then proceeds to the next point 
and repeats this operation until all the points have been measured, 
marked and recorded. 
DETAILED DESCRIPTION 
Hie operator's console contains all the controls necessary for 
the proper operation of the equipment (See Figure 2). They include 
a monitor scope upon which may be viewed either or both of the images 
being scanned on the comparator tables and binocular viewer for 
stereoscopic viewing of the conjugate imagery. An electronic cross 
hair or reticle is displayed on the monitor scope and electronic 
dots representing the floating marks are displayed on the stereoviewer. 
The operator's console also includes a visual display of the x, y 
coordinates for both tables, adjustments on the y-axis to the marking 
system, electronic controls for the scan and viewing system, and a 
joy stick drive control. A reference table and scanner are attached 
to one side of the operator's console (See Figure 3). The reference 
unit contains a small mechanical comparator and an electronic scan 
system, the scanner being a duplicate of the systems used on the 
comparator tables. The reference unit is used to automatically 
transfer control point information stored and presented on small 
glass plate chips to diapositives on the comparator tables. 
Each comparator unit contains an x-y air-bearing table, a 16X 
optical system, a scan system, marking units, servo motors, and 
associated electronic circuitry (See Figure 4). The air-bearing